Besides their well known antimalarial activities, artemisinin-based drugs such as artemisinin (ART), dihydroartemisinin (DHA), artemether (ARM), and artesunate (ARS) have been reported recently to be also endowed of cytotoxic properties through induction of apoptosis (Singh N. P., et al., Anticancer Res., 2004, 24, 2277; Nam W., et al., Head Neck, 2007, 29, 335).
Even if DHA possesses some cytotoxic properties, the latter are usually observable at relatively high drug concentration. Over the past few years, ART derivatives have emerged because endowed of more pronounced cytotoxic properties than DHA itself, against a wide range of cancer cells suggesting some potential for the treatment of various cancers such as human hepatocellular carcinoma (Hou J., et al., Clin. Cancer Res., 2008, 14, 17, 5519), leukemia (Lu J. J., et al., Canc. Biol. Ther., 2008, 7, 7, 1017), prostate cancer, non-small cell lung cancer (Lu Y. Y., et al., J. Biomed. Sci., 2009, Feb. 2, 16:16), pancreas (Chen H., et al., Anti-Cancer Drugs, 2009, 20, 2, 131) and cervical cancer (Disbrow G. L., et al., Cancer Res., 2005, 65, 23, 10854).
It has been shown that compositions of some known antimalarial and various chemotherapeutics can lead to improved cytotoxic combinations. For example, ARS and tyrosine kinase inhibitor OSI-774 produce mainly additive effect on glioblastoma multiforme cell lines (Efferth T., et al., Biochem. Pharmacol., 2004, 67, 9, 1689); ARS and the anthracycline intercalating agent doxorubicin showed synergistic activity on leukemic T-cells (Efferth T., et al., PLoS One, 2007, 2, 1, e693), the anti-CD20 antibody rituximab potentiates the cytotoxic effect of ARS at high concentrations (Sieber S., et al., Int. J. Oncol., 2009, 35, 1, 149). Lately, a clinical trial aimed at comparing the efficacy of a cocktail containing vinorelbine and cisplatin with that of said cocktail in combination with ARS was reported. The combination treatment did not provide any improvement in the short term survival rate, nor in the mean survival time or in the one year survival rate, thus failing to demonstrate any benefit over the single cocktail regimen on these important end point (Zhang Z. Y., et al., J. Integrative Med., 2008, 6, 2, 134).
WO2004/071506 reported that ART could be used for treating tumours induced by oncogenic viruses and for treating viral infections. The inventors also reported that combinations of ART with further anti-cancer drugs could be used favourably. However, no biological data regarding such combination treatment were reported to support the alleged synergistic activity.
On another side, DHA and gemcitabine showed a modest 1.2 fold increase in inhibition of proliferation of HepG2 and Hep3B hepatoma cells (Hou J., et al., Clin. Cancer Res., 2008, 14, 17, 5519).
Besides those disclosures, some contradictory data also appeared in the literature. Synergistic effects between DHA and the well known HDAC inhibitor sodium butyrate have been reported (Singh N. P., et al., Anticancer Res., 2005, 25, 6B, 4325). It is noteworthy that these experiments were all conducted in the presence of 12 μM of holotransferrin, which, as an iron-carrying protein, acted to enhance iron penetration into the cells. This phenomenon is known to improve DHA reactivity by enhancing radical generation from the peroxy moiety (Disbrow G. L., et al., Cancer Res., 2005, 65, 23, 10854). However, the same authors have also disclosed previously in a patent application (WO199634602) that DHA and holotransferrin alone proved to lead to enhanced cytotoxic activity on MOLT-4 lymphoblastoid cells as well as in a canine mast cells carcinoma. Strangely, if the paper from 2005 highlights the fact that 10 μM DHA in the presence of 12 μM of holotransferrin had no effect on Molt-4 cells (FIG. 1C, page 4327), the same experimental conditions used in the patent application were reported to lead to 75% reduction in cell count at 8 hours. U.S. Pat. No. 5,578,637 also reported combinations involving endoperoxide-containing compounds wherein the presence of an iron enhancing agent was mandatory.
EP1658844 reports the outcome of a treatment therapy of two patients affected by uveal melanoma involving the use of ARS in combination with dacarbazin in the presence or absence of a concomitant iron therapy, the latter was aimed at increasing the efficacy of ARS. Meanwhile the first patient, who did not receive the supplementary iron medication, died 23 months after entry into stage IV according to AJCC (Balch C. M., et al., J. Clin. Oncol., 2001, 19, 16, 3635), the second patient, who received the supplementary iron medication, was still alive at the time this patent application was filed.
WO200213826 disclosed combinations of the anti-malarial agents chloroquine, hydroxychloroquine and primaquine with the anti-cancer agents cisplatin and doxorubicin. Such combinations resulted in a better anti-cancer efficacy on few cell-lines, above all when the anti-malarial drug was used in high concentration. Quinine derivatives, and in particular hydroxychloroquine have recently been reported to block autophagy, the latter being recognized to be a tumour resistance mechanism allowing cancer cells to survive in stress conditions (Rubinsztein D. C., et al., Nature Rev. Drug Disc., 2007, 6, 304). Furthermore, the difference in the mechanism of action of quinine-like drugs and artemisinin-like drugs is reported (Jung M., et al., Curr. Med. Chem., 2004, 11, 10, 1265; Meshinick S. R., et al., Microbiol. Rev., 1996, 60, 301; Wu W. M., et al., Chem. Soc. Chem. Commun., 1996, 2213; Wu W. M., et al., J. Am. Chem. Soc., 1998, 120, 3316). Jung M., et al. cited herein above also reported that novel C-12 non-acetal type deoxyartemisinin were found to possess exceptionally high in vitro antitumour activity. Such derivatives are structurally unrelated to the compounds of the present invention.
Nevertheless, other pharmaceutical combinations involving either ART, DHA or ARM and a second chemotherapeutic agent chosen from the group consisting of a camptothecin derivative, or a PARP-1 inhibitor, or an intercalating DNA agent, or an alkylating agent have never been reported to produce synergistic effects toward the treatment of cancer diseases.
Camptothecin derivatives originated from the discovery more than forty years ago of the alkaloid camptothecin, further referred to as CPT. The latter is reputed to be endowed of potent and wide spectrum anti-cancer activity. A lot of efforts, from numerous medicinal chemistry groups, have been devoted at improving the physico-chemical properties of CPT itself. Potent CPT derivatives can be found for example in EP1044977 (filed in the name of the Applicant). Zunino F., et al. also nicely reviewed the latest advances in the field of CPT derivatives (Zunino F., et al., Curr. Pharm. Des., 2002, 8, 2505).
A promising role of PARP-1 inhibition in oncology was established on the basis that BRCA1 and BCRA2 knock-out cell lines were found to be highly sensitive to PARP-1 inhibitors, the latter provoking cell death. BRCA1 and BCRA2 protein mutations can lead to a major risk of breast, ovary prostate and pancreas cancers (e.g., MK-4827, Jones P., et al., J. Med. Chem., 2009, 52, 22, 7170). WO2006110816 reported PARP inhibitors, among which ABT-888, endowed with anti-inflammatory properties besides possessing anti-proliferative properties.
PARP-1 inhibitors have also been reported to enhance the cytotoxic activities of anti-cancer drugs such as topoisomerase-I inhibitors (Delaney C. A., et al., Clin. Cancer Res., 2000, 6, 2860-2867) and cisplatin (Miknyoczki S. J., et al., Mol. Cancer Ther., 2003, 2, 371). Combination therapy on BRCA2/p53 deficient mice developing mammary tumours involving the use of PARP-1 inhibitor AZD2281 (Menear K. A., et al., J. Med. Chem., 2008, 51, 6581) together with carboplatin was reported lately. Such a study showed no advantage over carboplatin monotherapy. Only the time to tumour relapse was increased when the PARP-1 inhibition was prolonged (Hay T., et al., Cancer Res., 2009, 69, 9, 3850). The patent application WO2008063644 (Cephalon) reports that some carbazole derivatives as PARP-1 inhibitors cause radio-sensitization in human glioblastoma related xenograf model. A clinical trial (NCT00920595) is currently recruiting patient for a study regarding a combination therapy against solid tumours involving a PARP inhibitor and the methylating agent temozolomide.
Intercalating DNA agents such as anthracycline or acridine derivatives have been known and used for years in the treatment of various form of cancers; the best known derivatives being doxorubicin, daunorubicin, and dactinomycin.
Treatment of cancer remains largely unsatisfactory because of drug resistance phenomenon or dose-limiting cytotoxicity. Therefore, new treatments involving potent and safer drugs are highly desired to further increase the chance of finding an adequate therapies against cancer diseases.